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Jianhua Zhang, Vivien Coulson-Thomas, Yong Yuan, Osamu Yamanaka, Hongshan Liu, Winston Kao; Lumican Is Required for Epithelium Migration during Healing of Corneal Epithelium Debridement. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2568.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Lumican, a member of small leucine rich proteoglycan (SLRP), is a matrikine besides serving as an extracellular matrix ECM component and regulator of collagen fibrillogenesis. Previous studies have shown that lumican promotes healing of corneal epithelial debridement via enhanced epithelial cell proliferation. The current study attempts to determine whether lumican plays an additional role in promoting corneal wound healing by enhancing epithelial cell migration.
Methods: Adult lumican null (Lum-/-), hemizygous (Lum+/-) and wild type (Lum+/+) mice were anesthetized and subjected to circumvent corneal epithelium debridement (2 mm in diameter) with Agerbrush®. Corneas were isolated at different intervals (0 through 6 h) and subjected to whole mount IF in order to characterize the epithelial cell migration by analyzing the expression and localization of cytoskeletal and adherens components, e.g., paxillin, etc. The role of lumican on stress fiber and filopodia formation were confirmed in vitro using a scratched wound model of cultured human telomerase-immortalized corneal epithelial (HTCE) cells.
Results: Whole mount staining with phalloidin revealed a decrease in the migrated corneal epithelial sheet in Lum-/- mice, from 10 and 105 µm in Lum+/+ mice to 0 and 5 µm in Lum-/- mice after 1 and 6 h, respectively. Immunofluorescence staining revealed high expression levels of paxillin throughout the epithelium with dense staining at the wound edge in Lum+/+ mice, however, Lum-/- mice presented very low expression levels of paxilin and a subtle increase in paxilin expression was restricted to the immediate wound edge. Moreover, paxilin staining revealed cellular projections in epithelial cells at the wound edge which were polarized into the wounded area solely in the Lum+/+ mice. The in vitro scratch wound assay of HTCE cells revealed that the addition of solely lumican to cells maintained in basic medium (in the absence of growth factors) enhanced stress fiber formation with filopodia projected to the wounded area to the same extent as that observed in complete medium.
Discussion: Our observation suggests that lumican plays a critical role in promoting wound healing via both the enhancement of cell locomotion and proliferation. Further studies are needed to determine the molecular and cellular mechanism by which lumican promotes wound healing.
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